Transcript Document

UM-OLSR
OLSR routing protocol in NS2
郭祐暢
695430044
Outline
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Brief overview of OLSR
MPR selection algorithm
UM-OLSR install
Example
UM-OLSR code
Classification
Ad Hoc Routing
Protocols
reactive
Source-Initiated
On demand
proactive
Table driven
DSDV
OLSR
TBRPF
CGSR
AODV
DSR
LMR
TORA
ABR
SSR
Optimized Link State Routing Protocol
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Proactive & Table-driven
Link State Routing
 Each node expands a spanning tree
 Each node can obtain the whole network topology
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Utilizes a technique to reduce message flooding
 MultiPoint Relaying (MPR)
Optimized Link State Routing Protocol
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Each node periodically floods
status of its links
Each node re-broadcasts link state
information received from its
neighbors
Each node keeps track of link state
information received from other
nodes
Each node uses above information
to determine next hope to each
destination
24 retransmissions to
diffuse a message up to 3
hops
Retransmission node
Optimized Link State Routing Protocol
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Only selected neighbors (MultiPoint
Relays, MPRs) retransmit
messages
Select MPRs such that they cover
all 2hop neighbors
2-hop neighbors taken from
neighbors' HELLO messages
11 retransmission to
diffuse a message up to 3
hops
Retransmission node
- MPR
Optimized Link State Routing Protocol
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Three main modules
 Neighbor/link sensing
 Provide topology information up to two hops
 MPR selector information notification
(“A select B as A’s MPR” in HELLO message to B)
 Optimized flooding/forwarding
 MPR set to cover all the two hop neighbors
 MPR selector set: set of nodes that select me as one of their
MPR set
 OLSR-Messages from MPR selector set are to be forwarded
 Link-State messaging and route calculation
 Topology table
 Route table
MPR selection
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Each node select a set of MPR
Selectors
 Who can be a MPR Selectors
of node N ?
Y
N
 one-hop neighbors of N
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MPR set of Node N (Rules)
X
 Set of MPR’s is able to
transmit to all two-hop neighbors
 Link between node and it’s
MPR is bidirectional.
M
D
Z
A
B
Multipoint Relays (MPR)
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Every node keeps a table of routes to all known
destination through its MPR nodes
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Every node periodically broadcasts list of its MPR
Selectors (instead of the whole list of neighbors).
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Upon receipt of MPR information each node recalculates
and updates routes to each known destination
MPR selection algorithm
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Each point u has to select its set of MPR.
 Goal :
Select in the 1-neighborhood of u (N1(u)) a set of nodes as
small as possible which covers the whole 2-neighborhood of
u(N2(u)).
 Step 1: Select nodes of N1(u) which cover isolated points
of N2(u).
 Step 2: Select among the nodes of N1(u) not selected at
the first step, the node which covers the highest
number of points of N2(u) and go on till every
points of N2(u) are covered.
MPR selection algorithm
u
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First step: Select nodes in N1(u) which cover “isolated points” of
N2(u).
MPR selection algorithm
u
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Second step : Consider in N1(u) only points which are not already
selected at the first step NPR1(u) and points in N2(u) which are not
covered by the NPR1(u) . While there exists points in N2(u) not
covered by the selected MPR, select in N2(u), the node which covers
the highest number of non-covered nodes in N2(u).
MPR selection algorithm
u
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Final：MPRs
Installation
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Download UM-OLSR 0.8.8 from
http://masimum.dif.um.es/?Software:UM-OLSR
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Ns2.27、2.28、2.29 / UM-OLSR 0.8.7、0.8.8
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Copy um-olsr-0.8.8.tgz to ns-allinone-2.29/ns-2.29/
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$ cd ns-allinone-2.29/ns-2.29/
$ tar zxvf um-olsr-0.8.8.tgz
$ ln -s ./um-olsr-0.8.8 ./olsr
$ patch -p1 < olsr/um-olsr_ns-2.29_v0.8.8.patch
$ ./configure
$ make
Example
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Download olsr_example.tcl from
http://masimum.dif.um.es/um-olsr/olsr_example.tcl
OLSR
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Hello message one hop for
 Two hop topology information
 MPRs
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Transmit two hop top topology information
 By MPRs
 TC message
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Complete Topology Information
 Shortest Path Tree calculation (Dijkstra)
 Routing table build
TC message
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TC – Topology control message:
 Sent periodically. Message might not be sent if there are
no updates and sent earlier if there are updates
 Contains:
 MPR Selector Table
 Sequence number
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Each node maintains a Topology Table based on TC
messages
 Routing Tables are calculated based on Topology tables
Topology Table
Destination
address
Destination’s
MPR
MPR Selector
sequence
number
MPR Selector in
the received TC
message
Last-hop node to the destination.
Originator of TC message
Holding time
TC message
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Upon receipt of TC message:
 If there exist some entry to the same destination with
higher Sequence Number, the TC message is ignored
 If there exist some entry to the same destination with lower
Sequence Number, the topology entry is removed and the
new one is recorded
 If the entry is the same as in TC message, the holding time
of this entry is refreshed
Routing Table
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Each node maintains a routing table to all known
destinations in the network
 Routing table is calculated from Topological Table, taking
the connected pairs
 Routing table:
 Destination address
 Next Hop address
 Distance
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Routing Table is recalculated after every change in
neighborhood table or in topological table
UM-OLSR File List (Header)
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OLSR.h
 header file for OLSR agent and related classes
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OLSR_pkt.h
 contains all declarations of OLSR packets and messages
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OLSR_printer.h
 includes all printing functions related to OLSR
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OLSR_repositories.h
 defined all data structures needed by an OLSR node
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OLSR_rtable.h
 header file for routing table's related stuff
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OLSR_state.h
 declares and defines internal state of an OLSR node
UM-OLSR File List
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OLSR.cc
 Implementation of OLSR agent and related classes
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OLSR_printer.cc
 Printing functions used for debugging and tracing are implemented
in this file
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OLSR_rtable.cc
 Implementation of our routing table
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OLSR_state.cc
 Implementation of all functions needed for manipulating the
internal state of an OLSR node